It is known that the reaction mixture at the outlet of an oxychlorination reactor mainly comprises the EDC (1,2-dichloroethane), water gas and recycling gas (carbon dioxide, nitrogen, argon) and has a temperature of 220.degree. C. at a pressure of approx. 4.2 bar. Because friction occurs in the catalyst, the stream leaving the reactor is passed through a micron filter to catch the dust discharged by the catalyst and/or through a cyclone and is then fed into the quenching column. The column is used for washing the hydrogen chloride out of the reactor discharge stream and for neutralizing it and for promoting the alkaline decomposition of chlorinated by-products, such as chloral.
Sensible heat is withdrawn from the reaction mixture in the quenching column. The temperature at the head of the column is 102' C. The reaction products., water and EDC, are condensed in the raw EDC condenser downstream of the column before being individually separated and removed from the recycling gas in an EDC settling vessel. The water obtained and the caustic soda (which serves to neutralize and decompose by-products) are fed back to the quenching column as reflux at a temperature of approx. 400C. A part-stream, approximately equal in volume to that of the reaction water, is drawn off at the bottom of the quenching column and fed to a waste water treatment stage.
A sufficient quantity of liquid must be constantly supplied to the quenching column to ensure that it functions correctly. The column discharge can be split into two constituents: one being the reaction water which enters the column with the reactor discharge stream prior to being condensed in the raw-EDC condenser; the other being the water from the column, which is evaporated using some of the sensible heat from the reactor discharge stream before being condensed in the raw-EDC condenser.
This last constituent is thus in constant circulation as a result of the continuous evaporation and subsequent condensation processes- most of the sensible heat at the reactor outlet is dissipated by cooling water.